Neutral Hydrogen Observations of Low Surface Brightness Galaxies around M101 and NGC 5485

Abstract

We present atomic hydrogen (H i ) observations using the Robert C. Byrd Green Bank Telescope along the lines of sight to 27 low surface brightness (LSB) dwarf galaxy candidates discovered in optical searches around M101. We detect H i reservoirs in five targets and place stringent upper limits on the remaining 22, implying that they are gas-poor. The distances to our H i detections range from 7 to 150 Mpc, demonstrating the utility of wide-bandpass H i observations as a follow-up tool. The systemic velocities of three detections are consistent with that of the NGC 5485 group behind M101, and we suggest that our 15 nondetections with lower distance limits from the optical are associated with and have been stripped by that group. We find that the gas richness of confirmed M101 satellites are broadly consistent with those of the Milky Way satellites, as well as with those of satellites around other hosts of comparable mass, when survey completeness is taken into account. This suggests that satellite quenching and gas stripping proceed similarly around halos of similar mass, in line with theoretical expectations.